Liquid composition containing rubber



Patented Apr. 28, 1936 2,038,556

UNITED STATES PATENT OFFICE Carleton Ellis, Montclair, N. J assignor to Standard Oil Development Company, a corporation of Delaware.

No Drawing. Application December 24, 1932,

Serial No. 648,825

Claims. (01. 134-17) The present invention relates to improved as the partial pressure of hydrogen. This rate solvent compositions and more specifically to may be suitably about 1.5 to 4 volumes of oil per compositions which are used as-rubber cements. volume of catalyst-filled reaction space per hour.

In the making of such compositions the crepe The catalysts preferably comprise the oxides rubber, or other forms of crude rubber, or other or sulphides of the elements of the 6th group to- 5 rubber stock is dissolved in a hydrocarbon mixgether with suitable promoters of the alkaline ture of the character more fully described below. earth or earth oxides. Such catalysts are insen- This hydrocarbon solvent preferably possesses a sitive to sulphur poisoning and are suitably clashigher boiling range and higher flash point than sified as sulphactive.

{ benzol (customarily used as a rubber solvent) The hydroformed petroleum product obtained 10 and furthermore does not exhibit those peculiar thereby possesses highly desirable solvent powers toxic properties commonly attributed to benzol. throughout its boiling range. For my particular In addition the preferred solvent also exhibits purpose, however, I prefer to use fractions posthe following unusual property, namely, that sessing adequate volatility, for example, boiling over a considerable range of viscosity, solutions in a range which lies within points included beof rubber therein show a higher rubber content tween the temperatures 200 and 420 F., though than do solutions of the same viscosity but which fractions having an initialboiling point of less are made with benzol. than 200 F. or higher than 420 F. are not. ex-' This unusual property of the hydroformed eluded. The requirements of the user respecting 2Q solvents is of particular importance in the manthe desired rate of drying of a rubber cement 2o ufacture of rubber cements, as it allows more of may be decisive in the determination of boiling the cementing. material to be employed per given range, a lower boiling range being selected when volume of solvent, thus aiding in the cementing a higher rate of volatility is needed. operation. At the same time the viscosity of the In making solutions of rubber in these hydro- A solution is not increased, and an even flow or formed solvents, a preferred procedure is to distribution of the cementing composition may masticate the crepe or other crude rubber on be secured. milling rolls, and then kneading with the solvent. The preferred solvent is a synthetic hydro- Or the crude rubber, after masticating, may be formed vehicle, derived from petroleum or its placed in contact with the solvent and either alvarious liquid distillation or extraction products. lowed to stand or the mixture of rubber and These hydroformed solvents may be produced solvent agitated until solution takes place. Confrom petroleum dist'llate's such as burning oil siderable time is required to secure solution when or gas oil, and in general from hydrocarbon oils the crude rubber is merely allowed to stand in of a boiling range including that of gasoline and contact with the solvent, while the time is very '1, also of ranges exte d g up to about 650 to 700 materially shortened by either agitation or .35

F. or somewhat higher. In producing such kneading.

solvents a petroleum distillate oil may be passed By way of illustrating the peculiar solvent in the vapor phase with free hydrogen over a power of these hydroformed solvents towards suitable catalyst at a pressure in excess of 20 rubber the following examples are given:

40 atmospheres (preferably 50 to 200 atmospheres Three hydroformed solvents were used; hydro- 40 or higher) desirably at a temperature above 900 solvent (1), having a boiling range of 200 to 275 F. and preferably within the range of about 930 F.; hydro-solvent (2), having a boiling range of to 1050 F. with a suitable partial pressure of 275 to 365 F.; and hydro-solvent (3), having a hydrogen n time of t ct to secure reconboiling range of 365 to 419 F. For comparative stituting of the hydrocarbon oil molecules withpurposes the results obtained when using benzene out necessarily forming appreciable amounts of (benzol) and. an ordinary petroleum solvent polyme i ed o ooky material- The hydrogen supnaphtha (boiling range 197 to 270 F.) not subplied is preferably within the range of about 1000 jected. to the hydrogen treatment, are included to 4000 cubic feet per barrel of feed oil, the also. The rubber was'smoked sheet, milled to run 5() amount generally depending upon the gravity smooth on the rolls. Stock solutions were preand boiling range of the charging stock. A greatpared by placing 7.5 grams of rubber in 150 cc. of er proportion of hydrogen may be used with suitthe solvent and the mixture shaken until complete able variation in feed rate, temperature and pressolution took place. Solutions of lower concensure. The feed rate depends upon the reaction trations of rubber (within dilution of commercial temperature, and other operating conditions such significance) were prepared by diluting the origi- 55 nal solutions with the requisite quantity of additional solvent. The following table gives the Saybolt viscosity at 100 F. for the diluted solutions so prepared.

It will be readily seen from the above data that, within a range of useful concentrations, solutions of rubber in the hydroformed solvents are much less viscous than benzol solutions of the same rubber content and very much less viscous than petroleum solvent naphtha solutions of the same rubber content. Another way of stating this is that for solutions of the same viscosity more rubber may be dissolved in the hydroformed solvents than in either benzol or petroleum solvent naphtha. For example: the concentration of rubber required in benzol for a 200 second viscosity solution can be calculated at about 2 grams per 100 00., while for hydroformed solvent (1) over 3 grams per 100 cc. are required. For the same viscosity relatively much less rubber is present in the case of the ordinary petroleum solvent naphtha. Within useful concentrations, therefore, volatile hydroformed petroleum solvents provide the means of applying a greater weight of rubber with less solvent.

In consequence excellent rubber-containing compositions may be made which may be utilized as rubber cement in the shoe industry and elsewhere, as coating compositions to produce rubberized fabrics, waterproof material, and the like, and for various other purposes. The rubber solutions in hydroformed solvents may also be used for the preparation of dipped goods. The main requirement for such a purpose is the use of a solvent having a uniform evaporation rate, a nonobjectionable odor, and a satisfactory capacity to dissolve rubber. The hydroformed solvents possess such properties to a noteworthy degree. To such compositions there may be added resins, animal, vegetable or mineral oils, as well as other modifying agent, including pigments, fillers, sulphur and other Vulcanizing agent, accelerators of vulcanization, anti-oxidants, and the like. In some cases other solvents may be incorporated with the hydroformed vehicle, including ordinary petroleum naphthas,volatile coal tar solvents, and so forth. However, for most purposes it is desirable to use as the sole solvent the hydroformed vehicle for hygienic reasons as well as because of its pleasant odor. Additions of solvents such as certain of those derived from coal tar, likewise hydrogenated naphthalene such as tetralin, tend to give the composition an unpleasant odor which would be objectionable to workmen, especially in confined places.

While I have referred principally to crepe rubber and other forms of raw rubber, it is understood that I may employ in some cases rubber which has been slightly vulcanized so that its solubility is not particularly reduced, also some forms of reclaimed rubber and various other members of the rubber family, including balata, and the like, in so far as their solubility permits such use. Mixtures of various rubber materials may be used in other cases. The product known as depolymerized rubber, which is rubber that has been treated with acid or other substance to reduce its degree of polymerization and increase its solubility, may be employed in solution in the hydroformed vehicle, with or without other rubber stocks.

My invention is not to be limited by any of the above examples given for illustrative purposes nor by any theory regarding the solvent characteristics of the hydroformed solvents.

What I claim is:

1. A rubber composition comprising rubber in solution in a solvent produced by destructive hydrogenation of a petroleum distillate having a boiling range including that of gasoline, burning oil and gas oil and extending up to about 700 F., at a temperature above about 900 F. and a pressure in excess of atmospheres in the presence of a hydrogenation catalyst.

2. Composition according to claim 1 in which the solvent boils in a range between the approximate limits of 200 and 420 F.

3. Composition according to claim 1 in which the solvent boils in a range between the approximate limits of 200 and 275 F.

4. Composition according to claim 1 having a 100 F. Saybolt viscosity between the approximate limits of 50 and 200 seconds.

5. Composition according to claim 1 in which the solvent used has a viscosity corresponding to substantially less than 250 seconds Saybolt at 100 F. for 2.5 grams of smoked sheet rubber, milled to run smooth on the rolls, per 100 cc. of solution and substantially less than 130 seconds Saybolt at 100 F. for a concentration of 1.67 grams of the same smoked sheet rubber per 100 cc. of solution.

CARLE'I 'ON ELLIS. 

